A wide variety of therapeutic techniques have been developed to correct or inhibit vascular diseases. Coronary artery disease (CAD), for example, is an adverse condition of the heart in which the blood flow to the heart muscle is partially or totally restricted by occlusive material in the coronary arteries which narrows the blood flow lumen. The occlusive materials deprive portions of the heart muscle of essential oxygenated blood.
CAD may be treated by a surgical technique referred to as coronary artery bypass graft (CABG) surgery. This surgical procedure involves supplementing blood flow to the heart muscle by grafting a non-native conduit such as a saphenous vein graft (SVG) to the heart. A first end of the SVG is connected to the ascending aorta (proximal to the occlusive material) and the other end is connected to the artery distal of the occlusive material. Although this technique has been useful for treating CAD in native coronary arteries, it is not uncommon for occlusive material to form over time in the SVG thereby necessitating additional therapy.
Percutaneous translumenal coronary angioplasty (PTCA) has gained wide acceptance as an effective and less invasive alternative to CABG surgery in certain patient groups. The PTCA procedure involves the use of an angioplasty balloon catheter, several types of which are well known in the art. The balloon catheter is inserted into the body via the femoral artery and navigated to the coronary arteries assisted by a guide catheter and (usually) a guide wire. The balloon is positioned across the restriction in the artery and subsequently inflated. The inflated balloon widens the restriction and restores blood flow to portions of the heart muscle previously deprived of oxygenated blood.
A PTCA balloon catheter is typically about 140 to 150 cm long and has a manifold at its proximal end and a balloon at its distal end. The manifold facilitates connection to an inflation device which is used to inflate and deflate the balloon. A PTCA balloon catheter also includes an inflation lumen extending through its entire length to facilitate the delivery of inflation fluid to and from the balloon. Depending on the type of catheter used, an inflation lumen may be circular in cross section or it may be annular in cross section. Some catheters have an inflation lumen which is circular at the proximal end of the shaft and annular at the distal end of the shaft. Since, PTCA catheters are relatively small in profile in order to facilitate navigation through the vascular system, the inflation lumen extending through the shaft is proportionately small. The long length of a typical inflation lumen in combination with its relatively small size create a significant resistance to the flow of inflation fluid. Consequently, the time required to inflate and deflate the balloon is proportionately long. Because flow rates are proportional to pressure, the drag on the inflation fluid is particularly noticeable during balloon deflation when the maximum possible pressure gradient is 14.7 psi. The deflation time is significant because an excessively long deflation time will compromise the treating physician's ability to relieve aschemia and/or reestablish blood flow across the occlusion being dilated. Furthermore, the compliance of the inflation fluid, the inflation device and the entire structure defining the fluid path add to the delay in deflation and inflation. The compliance of the fluid system reduces the immediate responsiveness of the balloon to actuation of the inflation device.
An inflation device is typically capable of inflating to pressures of about 300 psi, and is capable of drawing a near perfect vacuum (perfect vacuum=-14.7 psi). An inflation device is usually in the form of a modified 20 cc syringe and typically includes a threaded plunger with a handle and lock mechanism, and a pressure gauge. Due to its size and weight, a typical inflation device is extremely bulky as compared to a PTCA catheter.
Prior art balloon dilation catheters and inflation devices have certain disadvantages which are desirable to overcome. For example, it is desirable to reduce the inflation/deflation time of a balloon catheter and increase the immediate responsiveness of the balloon. This would allow for a more rapid balloon deflation and thus relieve aschemia and other adverse reactions to prolonged balloon inflation. Reducing inflation/deflation time would also allow for more effective use of the pulsating balloon technique. Eliminating a significant amount of the fluid system compliance would allow the treating physician to better "feel" the response of the vascular restriction to the inflation of the balloon. These desirable aspects would improve the treating physician's capabilities to treat CAD.
It is also desirable to eliminate the need to use a bulky inflation device. Eliminating the need for an inflation device would, for example, reduce the number accessory devices needed in a procedure, reduce the number prepping procedures required, reduce the necessary storage space, and reduce the amount of medical waste generated in a procedure. All of these benefits would ultimately save a significant amount of time and expense on behalf of the treating physician, the medical support staff, the hospital and the patient.